Study on the low-temperature properties of pyrochlores Gd_(2)Hf_(2)O_(7) and Gd_(2)Zr_(2)O_(7), using crystal-field theory

摘要

The geometrically frustrated pyrochlores Gd_(2)Hf_(2)O_(7) (GdH) and Gd_(2)Zr_(2)O_(7) (GdZ) are easy planar anisotropic systems in which considerable single-ion crystal-field anisotropies of D_(3d) symmetry are found in the ground multiplet ~(8)S_(7/2) due to admixture of higher Russell-Saunders terms. The ~(8)S_(7/2) splits into 4 doublets with total CF splitting 9.9 K in GdH and 9.4 K in GdZ. The magnetic specific heat C_(mag) follows a conventional T~(3) behavior in GdH and an unconventional T~(4.6) behavior in GdZ down to 0.4 K.